In presentations, conferences, or the like, in some cases, there is used an image display system capable of displaying a display screen of a terminal such as a personal computer operated by each of a plurality of participants on a common screen area, which can be viewed by all of the participants. In International Patent publication WO2005/088602, there is proposed a technology of dividing the projection screen into a plurality of image areas, and arranging the images transmitted from a plurality of image generation devices to an image projection device to the respective image areas thus divided to thereby project the respective images at the same time. Japanese Patent No. 4010198 is another example of a related art document.
Incidentally, in presentations or conferences, in general, roles of the participants are replaced with each other flexibly such as a presenter and a speaker changed in a rotating manner. Therefore, in the case in which the display screens of the terminals of the respective participants are displayed on the common screen area thus divided, it is preferable in terms of effective presentation and invigoration of discussion that the operation of changing the layout of the common screen area can be performed efficiently. However, it is very much a situation in which a sufficient devise has not ever been provided to improvement of the convenience of such an image display system.